Physicochemical Characterization and Kinetic Modeling concerning Combustion of Waste Berry Pomace

Herein waste biomass (blackberry pomace) was physicochemically characterized along with its thermochemical products. This is coupled with the evaluation of the kinetic triplet (activation energy, pre-exponential constant, and the rate of reaction) and thermal predictions for the combustion process for the first time via the AKTS thermokinetics package. The main kinetic modeling method employed was the differential isoconversional analysis; however, the Flynn-Wall-Ozawa and ASTM E-698 methods were used as comparisons. The model was developed and validated from experimental DSC and TGA data, resulting in an excellent match (R2 = 0.99544 and 0.99194, respectively). The activation energies were evaluated using the ASTM-E698 method (88.64 kJ mol-1) and Flynn-Wall-Ozawa methods (50-140 kJ mol-1). The differential isoconversional method showed that activation energy values were in the range of 84-197 kJ mol-1 for the combustion of berry pomace. Isothermal predictions based on the model were indicated at temperatures of 560 and 600 °C; the reaction had achieved 100% completion (α = 1) after 30 and 6 min, respectively. For the nonisothermal prediction, the heating rates of 50, 75, and 100 °C/min have a two-stage rate profile with a maximum peak in the first stage of the reaction. Thereafter, the reaction rate increases once again but not to the same effect as the first initial stage. For instance, at 100 °C/min, stages 1 and 2 are reported as 0.005381 and 0.005148 s-1,respectively. Overall, this study demonstrates the success of the approach in modeling the thermochemical conversion of berry pomace as waste stream biomass.